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RF Based Home Automation Project

Radio Frequency or RF based Home Automation using 433 MHz RF transmitter & receiver  is a simple application oriented project, where you can control different home electrical and electronic appliances using RF Communication. With the advancement of technology, number of equipment and modern household appliances are increasing to make life easier and comfortable. Operating them manually is a tedious job and hectic sometimes. Life will become simpler if we can control devices like TV, fan, light or a music system with a remote from a distance just by pressing the button. This project deals with an interesting manner of automating the home appliances with the help of RF Communication Technology.

RF Based home Automation

Materials Required for RF controlled Home Appliances Project:

  • 433 MHz RF Transmitter and Receiver
  • HT12D Decoder IC
  • HT12E Encoder IC
  • 5V Relay Module (2Nos)
  • Push on Push Off Switch (2 Nos)
  • 1M ohm, 47K ohm Resistor
  • 7805 Voltage Regulator
  • 9V Battery (2Nos)
  • Bread Board (2Nos)
  • Connecting wire

433MHz RF Transmitter and Receiver Module:


Let me give brief intro to these RF modules before getting into the project. The term RF stands for “Radio Frequency”. A RF transceiver module will always work in a pair that is it needs a Transmitter and Receiver to send and Send data. A transmitter can only send information and a Receiver and can only receive it, so data can always be sent from one end to another and not the other way around.

The Transmitter module consists of three pins namely Vcc, Din and ground as shown above. The Vcc pin has a wide range input voltage from 3V to 12V. The transmitter consumes a minimum current of 9mA and can go as high as 40mA during transmission. The centre pin is the data pin to with the signal to be transmitted is sent. This signal is then modulated using the ASK (Amplitude Shift Keying) and then sent on air at a frequency of 433MHz. The speed at which it can transmit data is around 10Kbps.

The Receiver module has four pins namely Vcc, Dout, Linear out and Ground as shown above. The Vcc pin should be powered with a regulated 5V supply. The operating current of this module is less than 5.5mA. The pins Dout and Linear out is shorted together to receive the 433Mhz signal from air. This signal is then demodulated to get the data and is sent out through the data pin.



Need of Encoder and Decoders:

The RF modules can also function without the need of Encoder and Decoder modules. Simply power on both the modules with the corresponding voltage mentioned above. Now, make the Din pin on transmitter high and you will find the Dout pin on receiver also goes high. But, there is a big drawback in this method. You can have only one button on the sender side and one output on the receiver side. This will not help in building better projects, so we employ the encoder and decoder modules.

The HT12D and HT12E are 4-data bit encoder and decoder modules. This means that we can make (2^4 = 16) 16 different combinations of inputs and outputs. These are 18 pin IC’s which can operate between 3V to 12V input power supply. As said they have 4-data bit and 8-addresss bit, these 8 address bits has to be set same on both the encoder and decoder to make them work as a pair.

Out of the 4-data bit we will use only two in this project for demonstration purpose. You can use all four and control four AC Appliances with the same circuit. You just have to add two more Relay modules.

Circuit Diagram & Explanations:

There are two circuit Diagrams for this RF controlled Home Automation System, one for RF Transmitter as RF remote control for Home Appliances and one for RF Receiver where AC loads are connected. We have previously explained the RF Transmitter and Receiver circuit in detail.







As you can see the transmitter Circuit consists of the Encoder IC and the Receiver circuit consists of the Decoder IC. Since the transmitter does not need a regulated 5V we have directly powered it with a 9V battery. Whereas in the receiver side we have used a 7805 +5V voltage regulator to regulate 5V from the 9V battery.

Notice that the Address bits A0 to A7 on both the Encoder and Decoder IC are grounded. This means that they are both kept at address 0b00000000. This way they both share the same address and they will act as a pair.

The data pins D10 and D11 (Pin 12 and 13) are connected to switches on the Encoder side and to Relay modules on the decoder side. Based on the position of switch on the encoder side the information will be transferred to decoder and the corresponding light will get toggled.

The two relay modules are powered by the 5V supply provided by the 7805 Regulator and the input pin is connected to the decoder module. The loads are connected through the Relay module so that only when the relay is closed the connection to the load will be complete.

Note: Using a 9V battery to power the receiver set-up might not work properly since the battery is not powerful to supply enough current for relay module. In that case use a 12V battery or adapter.

Warning: High caution is required while handling 220V AC voltage. Make sure the connection is according to circuit and for beginners it is recommended to use junction box (Spike box) that has fuse in it. Also your wires should be of higher gauge so that it can carry the required current and do not connect loads that consume more than 8A current.






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